CN114402627A

CN114402627A - Port replicator

Info

Publication number: CN114402627A
Application number: CN202080063940.9A
Authority: CN
Inventors: 锡德里克·丰·拉姆; 赵向军; 尹爽; 穆图·纳加拉贾; 张涛; 杜亮; 亚当·埃德温·泰勒·巴拉特; 长虹·乔伊·蒋; 克劳迪奥·德桑蒂
Original assignee: Google LLC
Current assignee: Google LLC
Priority date: 2019-09-12
Filing date: 2020-09-10
Publication date: 2022-04-26
Also published as: US10992387B2; WO2021050785A1; US20210083770A1; EP4029164A1; TWI765346B; TW202119778A

Abstract

A method (600) of combining optical signals (104) from multiple optical fibers into a single optical signal includes receiving respective optical signals at respective optical signal receivers (305) optically coupled to respective trunk optical fibers. The method includes determining, by a corresponding optical signal receiver, when each respective optical signal is received. When receiving a corresponding optical signal, the method comprises: converting, by a corresponding optical signal receiver, the respective optical signal into a corresponding electrical signal (310); transmitting, by the corresponding optical signal receiver, the corresponding electrical signal to a corresponding input channel (318) of an electrical multiplexing device (316); the electrical multiplexing device is configured to select a corresponding input channel. Configuring the electrical multiplexing device to select the corresponding input channel causes the electrical multiplexing device to transmit the corresponding electrical signal to an electrical-to-optical converter (340), the electrical-to-optical converter (340) configured to convert the corresponding electrical signal back to a corresponding optical signal.

Description

Port replicator

Technical Field

The present disclosure relates to an Optical Line Terminal (OLT) port replicator.

Background

Fiber optic communication is an emerging technology for transmitting information from a source (transmitter) to a destination (receiver) using optical fiber as a communication channel. Fiber optic communications allow data to be transmitted over longer distances and higher bandwidths than other forms of communications. Companies use optical fiber to transmit telephone signals, internet communications, and cable television signals. A Passive Optical Network (PON) is a telecommunications technology for providing optical fibers to end consumers. A significant feature of a PON is that it implements a point-to-multipoint architecture, where a single fiber is able to serve multiple endpoints using a powerless fiber splitter. Passive optical networks are commonly referred to as the "last mile" between an Internet Service Provider (ISP) and a customer.

A PON comprises an Optical Line Terminal (OLT) located at a service provider central office (hub) and a plurality of Optical Network Units (ONUs) or Optical Network Terminals (ONTs) located near end users. A PON reduces the number of optical fibers and central office equipment required compared to a point-to-point architecture. In most cases, the downstream signal (i.e., from the OLT to the ONUs) is broadcast to all locations that share multiple fibers. The upstream signals (i.e., from the ONUs to the OLT) are combined using a multiple access protocol, typically Time Division Multiple Access (TDMA). Due to the topological structure of the PON, the transmission modes of the downstream and upstream are different. For downstream transmission, the OLT broadcasts optical signals to all ONUs in a Continuous Mode (CM). However, the use of CM by an ONU may cause optical signals transmitted from the ONU to overlap. Therefore, Burst Mode (BM) transmission is generally used for the uplink channel. BM transmission mode requires that the optical transmitter be turned on and off in a short time. In the BM, when an ONU is allocated a time slot and it has data to transmit, it transmits an optical packet.

Disclosure of Invention

One aspect of the present disclosure provides a method of combining optical signals from a plurality of optical fibers into a single optical signal. The method includes receiving respective optical signals at respective optical signal receivers optically coupled to respective trunk fibers. The method also includes determining, by the corresponding optical signal receiver, when each respective optical signal is received. When receiving a corresponding optical signal, the method comprises: converting the respective optical signals into corresponding electrical signals by corresponding optical signal receivers; transmitting, by a corresponding optical signal receiver, a corresponding electrical signal to a corresponding input channel of an electrical multiplexing device; and configuring the electrical multiplexing device to select the corresponding input channel. Configuring the electrical multiplexing device to select the corresponding input channel causes the electrical multiplexing device to transmit the corresponding electrical signal to an electrical-to-optical converter configured to convert the corresponding electrical signal back to a corresponding optical signal.

Implementations of the disclosure may include one or more of the following optional features. In some embodiments, a corresponding optical signal receiver includes a photodiode optically coupled to a corresponding trunk optical fiber, a transimpedance amplifier in communication with the photodiode, and a burst mode limiting amplifier in communication with the transimpedance amplifier. In these embodiments, the photodiodes convert respective optical signals to respective current signals, the transimpedance amplifiers convert respective current signals to respective electrical signals, and the burst mode limiting amplifiers indicate when respective optical signals are received. The photodiode may comprise an Avalanche Photodiode (APD) or a PIN diode.

In some examples, in response to determining when a corresponding optical signal is received, the burst mode limiting amplifier transmits a signal to the signal conditioning circuit causing the signal conditioning circuit to reset the transimpedance amplifier. The signal conditioning circuit may comprise a Complex Programmable Logic Device (CPLD) or a Field Programmable Gate Array (FPGA). In some embodiments, configuring the electrical multiplexing device to select the corresponding input channel includes transmitting, by the corresponding optical signal receiver, a signal detection indication to the channel selection circuitry, causing the channel selection circuitry to transmit the channel selection indication to the electrical multiplexing device. Here, the channel selection indication identifies a corresponding input channel of the electrical multiplexing device.

In some examples, the electrical-to-optical converter includes a burst-mode laser transmitter and/or a burst-mode laser transmitter that includes a Distributed Bragg Reflector (DBR) laser. The method may also include transmitting, by the electrical-to-optical converter, the respective optical signals to a port of an Optical Line Terminal (OLT). In some embodiments, the corresponding trunk optical fiber is optically coupled to a respective burst-mode laser transmitter of a respective Optical Network Unit (ONU).

Another aspect of the disclosure provides an optoelectronic optical converter comprising an electrical multiplexing device comprising one or more input channels, and an optical signal receiver optically coupled to a corresponding trunk optical fiber. In these embodiments, each optical signal receiver receives a respective optical signal from a corresponding trunk optical fiber and determines when the respective optical signal is received. When receiving the respective optical signal, the optical signal receiver converts the respective optical signal into a corresponding electrical signal, transmits the corresponding electrical signal to a corresponding input channel of the electrical multiplexing device, and configures the electrical multiplexing device to select the corresponding input channel. Configuring an electrical multiplexing device to select a corresponding input channel causes the electrical multiplexing device to transmit a corresponding electrical signal to an electrical-to-optical converter. Here, the electrical-to-optical converter converts the corresponding electrical signal back to a corresponding optical signal.

Implementations of the disclosure may include one or more of the following optional features. In some embodiments, a corresponding optical signal receiver includes a photodiode optically coupled to a corresponding trunk optical fiber, a transimpedance amplifier in communication with the photodiode, and a burst mode limiting amplifier in communication with the transimpedance amplifier. In these embodiments, the photodiodes convert respective optical signals into respective current signals, the transimpedance amplifiers convert respective current signals into corresponding electrical signals, and the burst mode limiting amplifiers indicate when respective optical signals are received. The photodiode may comprise an Avalanche Photodiode (APD) or a PIN diode.

The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

Drawings

Fig. 1A-1C are schematic diagrams of an example Passive Optical Network (PON) communication system.

FIG. 2 is a schematic diagram of an example communication system including an optical-to-electrical (O/E/O) converter.

Fig. 3A is a schematic diagram of an example optical-to-electrical (O/E/O) converter in communication with a PON.

FIG. 3B is a schematic diagram of an example O/E/O converter.

FIGS. 4A-4C are schematic diagrams of an O/E/O converter controller circuit.

Fig. 5A and 5B are schematic diagrams of an example optical signal splitter.

FIG. 6 is a flow chart of an example arrangement of operations of a method for combining optical signals from optical fibers into a single optical signal.

Like reference symbols in the various drawings indicate like elements.

Detailed Description

A significant feature of a Passive Optical Network (PON) is that it implements a point-to-multipoint architecture in which a single optical fiber is enabled to serve multiple endpoints using a powerless fiber splitter. A powerless fiber optic splitter may be referred to as a passive splitter. In a typical PON, one or more Optical Line Terminals (OLTs) are installed at a Central Office (CO) of an Internet Service Provider (ISP). An Optical Network Unit (ONU) is installed at each customer site of the CO remote from the ISP. An OLT typically has a fixed number of ports. Each port is optically coupled to an Optical Distribution Network (ODN). The ODN may include trunk fibers connecting the OLT ports to remote Optical Distribution Points (ODPs) containing unpowered fiber optic splitters. The ODP may be referred to as a Remote Node (RN). The split signal is distributed to ONUs installed at the subscriber site. The ONUs typically include burst-mode lasers to generate optical signals that are transmitted back to the OLT. The number of users served by one OLT port depends on many factors. These factors may include the distance from the OLT to the ODP or RN, the configuration of the passive optical splitter, and the number of users associated with each ODP, among others. Embodiments herein are directed to methods of combining optical signals from multiple optical fibers into a single optical signal. Embodiments herein are further directed to an optoelectronic-to-optical (O/E/O) converter capable of combining optical signals from multiple optical fibers into a single optical signal. In one example, the O/E/O converter is configured to reduce the number of OLT ports deployed by the ISP in the CO by extending the OLT ports across two or more trunk fibers optically coupled to two or more respective ODPs. Burst mode optical signals transmitted on two or more trunk optical fibers from an ONU are combined into a single optical signal by an O/E/O converter. Embodiments herein further relate to extending the range of an OLT port by increasing or restoring the strength of an optical signal transmitted from the OLT port to a remote location. These and other embodiments disclosed herein may also be used to implement and manage PONs supported by redundant OLT ports for improved reliability. Although the embodiments are described primarily in connection with PONs, the embodiments may similarly be used in connection with other optical communication systems.

Fig. 1A-1C depict an example optical communication system 100 that transmits communication signals 104 (e.g., optical signals) over communication links 110, 114a-n (e.g., fiber optic or line-of-sight free-space optical communications) between an Optical Line Terminal (OLT)120 housed in a Central Office (CO)200 and Optical Network Units (ONUs) 140, 140a-n (e.g., optical transceivers) associated with

users

150, 150a-n (also referred to as customers or subscribers). As shown in fig. 2A, the ONUs 140, 140a-n are typically located at the premises 152, 152A-n of the

users

150, 150 a-n. Customer Premises Equipment (CPE) is any terminal and associated equipment located at the premises 152 of the user 150 and connected to the operator telecommunications equipment at a demarcation point ("demarc"). A demarcation point is a point established in a house, building or complex for separating customer equipment from Service Provider Equipment (SPE). Some examples of CPEs include telephones, routers, switches, Residential Gateways (RGs), set-top boxes, fixed mobile aggregation products, home network adapters, or internet access gateways that enable user 150 to access the services of a communication service provider and distribute them around premises 152 of user 150 via a Local Area Network (LAN). In the illustrated example, ONU140 is a CPE.

In some embodiments, the optical communication system 100 implements an optical access network, such as a Passive Optical Network (PON)10, for example, for accessing and moving a fronthaul/backhaul network. Some examples of optical access networks include 10G-EPON, PON supporting 10 gigabit (XG-PON), symmetric PON supporting 10 gigabit (XGS-PON), next generation PON (NG-PON), and other PONs that comply with the International Telecommunication Union (ITU) standard. In some examples, the optical communication system 100 implements a point-to-point (pt-2-pt) PON 10 with a direct connection, such as an optical ethernet, in which a locally operating optical link 110 (e.g., fiber) extends all the way back to the OLT 120 at the CO 200, with each

customer

150, 150a-n being terminated by a separate OLT 120 a-n. In other examples, the optical communication system 100 implements a point-to-multipoint (pt-2-multi-pt) PON, wherein the shared OLT 120 serves a plurality of

customers

150, 150 a-n. For example, CO 200 includes at least one OLT 120 that connects an optical access network to an Internet Protocol (IP), Asynchronous Transfer Mode (ATM), or Synchronous Optical Network (SONET) backbone. Thus, each OLT 120 is an endpoint of the PON and converts between electrical signals used by service provider equipment and optical signals 104 used by the PON. As shown in fig. 1A, each OLT 120, 120a-n includes at least one transceiver 122, 122a-n, depending on the implementation of the optical access network. The transceivers 122, 122a-n are optically coupled to

corresponding OLT ports

124, 124 a-n. OLT 120 transmits optical signals 104 over corresponding feeder fibers 110 (e.g., fiber trunk 110) to corresponding Remote Nodes (RNs) 170 via corresponding ports 124.

Referring to FIG. 1B, remote node 170 may include band multiplexingA band multiplexer 160, the band multiplexer 160 being configured to demultiplex the optical signal 104_DAnd will demultiplex the optical signal 104_DAlong the corresponding distribution fibers 114, 114a-n to a plurality of

subscribers

150, 150 a-n. The band multiplexer 160 for multiplexing/demultiplexing may be an Arrayed Wavelength Grating (AWG)180, which is a passive optical device. In some examples, each CO 200 includes multiple OLTs 120, 120a-n, and each OLT 120 is configured to serve a group of users 150. In addition, each OLT 120 may be configured to provide signals in different services. For example, one OLT 120 provides services in an XG-PON and another OLT 120 provides services in an NG-PON.

CO 200 multiplexes signals received from multiple sources, such as video media distribution source 132, internet data source 134, and voice data source 136, and multiplexes the received signals into one optical signal 104 before transmitting the optical signal 104 to RN 170 through feeder fiber 110. Multiplexing may be performed by OLT 120 or a Broadband Network Gateway (BNG) located at CO 200. Typically, services are time division multiplexed at the packet layer. Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals on a common signal path by using different, non-overlapping time slots. Wavelength Division Multiplexing (WDM) enables point-to-multipoint communication in the PON 10 using a plurality of wavelengths λ. The OLT 120 provides a plurality of wavelengths through one optical fiber 110 to a band multiplexer 160 at the RN 170, and the band multiplexer 160 multiplexes/demultiplexes signals between the OLT 120 and the plurality of

ONUs

140, 140 a-n. Multiplexing combines several input signals and outputs the combined signal. Time Wavelength Division Multiplexing (TWDM) uses both time and wavelength dimensions to multiplex signals.

Referring to fig. 1C, the

customer premises

152, 152n may be a multi-dwelling unit (MDU), such as an apartment, or student dormitory. MDUs are characterized by high user density. Service providers recognize a huge potential return on fiber investment in an MDU environment. In some examples, the optical communication system 100 includes a plurality of optical transmitter/receiver or transceiver systems 120. In the example shown, one trunk fiber 110 sends a corresponding optical signal 104 from a corresponding OLT port 124 at CO 200 to a corresponding remote node 170, with a splitter 205 splitting the optical signal 104 and via a fiber feeder 114,114a-n will split optical signal 104_STo a number of

different MDUs

152, 152 a-n. Thereafter, each MDU 152 splits the signal 104 received by the corresponding fiber optic feeder 114_SAnd distributes the signal to a number of

ONUs

140, 140 a-n. The number of subscribers 150 served by one OLT port 124 depends on many factors including, but not limited to, the distance between OLT 120 and RN 170 and the configuration of passive optical splitter 205. The intensity of the optical signal 104 may be attenuated by the long trunk optical fiber 110. As described in more detail below, the intensity of the optical signal 104 received at the RN 170 may be increased or restored at one or more points between the CO 200 and the RN 170. In some embodiments, the branched optical signal 104_SIs increased at one or more locations between the RN 170 and the

customer premises

152, 152 a-n.

Fig. 2 depicts an example CO 200 that transmits/receives communication signals 104 (e.g., optical signals) to/from one or more Passive Optical Networks (PONs) 10, 10a-n of the optical communication system 100. An example PON 10 is discussed above in fig. 1A-1C. In the illustrated example, each PON 10 is served by a

respective port

124, 124a-n of an OLT 120 installed at a CO 200 of a service provider. One or

more OLT ports

124, 124a-n may be optically coupled to corresponding O/E/

O converters

300, 300 a-n. In some examples, each OLT port 124 is optically coupled to a corresponding O/E/O converter 300 and each O/E/O converter 300 is optically coupled to a corresponding set of trunk fibers 110, 110a-n (e.g., fiber or line-of-sight free-space optical communications), which distributes optical signals 104, 104a1-nN between the O/E/O converters 300 and the rest of the PON 10. For example, in the example shown, each trunk fiber 110, FT in the first set of trunk fibers 110a_a1-FT_aNDistributing the corresponding optical signals 104a1-aN between the O/E/O converter 300a and the rest of the PON 10 a; each trunk optical fiber 110FT of the second set of trunk optical fibers 110b_b1-FT_bNDistributing the corresponding optical signals 104b1-bN between the O/E/O converter 300b and the rest of the PON 10 b; each trunk fiber FT of the nth trunk fiber 110n set_n1-FT_nNThe corresponding optical signals 104n1-nN are distributed between the O/E/O converter 300n and the rest of the PON 10 n. In some examples, O/E/O converter 300 is installed at the COAt 200. The O/E/O converter 300 may also be installed at a location remote from the CO 200.

In some embodiments, each trunk fiber 110, FT_a1-FT_nNThe corresponding optical signals 104 are distributed to respective Remote Nodes (RNs) 170 (fig. 1A-1C) associated with a plurality of subscribers 150. Thus, each OLT port 124 is associated with a respective set of trunk fibers 110 and a respective set of RNs 170 serving a respective group of subscribers 150. In some examples, each O/E/O converter 300 receives upstream optical signals 104, 104a1-nN from the rest of the PON 10 via a corresponding set of trunk optical fibers 110, combines the received optical signals 104, 104a1-nN into a corresponding combined

optical signal

104, 104a-n, and transmits the combined

optical signal

104, 104a-n to a corresponding OLT 124 port of the OLT 120.

Referring to FIG. 3A, an example optical-to-electrical (O/E/O) converter 300 is depicted. The example O/E/O converter 300 is optically coupled to a corresponding OLT port 124 and includes an optical coupling to a corresponding trunk fiber 110, FT_a1-FT_aNTo the corresponding optical signal receiver 305. Each corresponding optical signal receiver 305 may include a photodiode 302 optically coupled to a corresponding one of the trunk optical fibers 110, a transimpedance amplifier (TIA)308 in communication with the photodiode 302, and a burst-mode limiting amplifier 312 in communication with the TIA 308. In some examples, each photodiode 302 is optically coupled to a corresponding trunk fiber 110 through laser optics (L/O) 304. The photodiode 302 may comprise an Avalanche Photodiode (APD)302 or a PIN diode 302. Other photodetectors may also be used.

In the example shown, each photodiode 302 (associated with a corresponding optical signal receiver 305) is coupled from a corresponding trunk optical fiber 110, FT_a1-FT_aNReceives the corresponding optical signal 104, 104a1-aN and converts the received optical signal 104 into a corresponding current signal 306. Thereafter, the corresponding TIA308 converts the respective current signal 306 into a corresponding electrical signal 310. In an example, TIA308 includes SemTech GN 7055B. Other transimpedance amplifiers may also be used. In some embodiments, the photodiode 302 and TIA308 associated with the corresponding optical signal receiver 305 are directly producibleA light sensor that generates a corresponding electrical signal 310. Thus, whether a photodiode-

TIA pair

302, 308 or a light sensor is implemented, for example, each corresponding optical signal receiver 305 is configured to receive a respective optical signal 104 via a corresponding trunk optical fiber 110 and convert the respective optical signal 104 to a corresponding electrical signal 310. In further embodiments, each corresponding optical signal receiver 305 is configured to convert the respective optical signal 104 into a corresponding electrical signal 310 when the optical signal receiver 305 determines that the respective optical signal 104 is received. In these embodiments, the corresponding burst-mode limiting amplifier 312 may determine when the corresponding optical signal 104 is received by the corresponding optical signal receiver 305. In an example, limiting amplifier 312 includes SemTech GN7153(SD) configured to output a Signal Detect (Signal Detect) indication upon receipt of a corresponding electrical Signal 310 converted by a corresponding TIA 308. In addition to or instead of limiting amplifier 312, the corresponding photodiode 302 and/or the corresponding TIA308 may optionally determine when the corresponding optical signal 104 is received by the corresponding optical signal receiver 305. Other methods of determining when the corresponding optical signal 104 is received may also be used. For example, when the optical signal receiver 305 implements a photosensor in place of the photodiode 302 and TIA308, the photosensor may be configured to determine when the corresponding optical signal 104 is received.

In some examples, the corresponding optical signal receiver 305 is configured to transmit the corresponding electrical signal 310 to the

corresponding input channel

318, 318a-n of the electrical multiplexing device 316 and configure the electrical multiplexing device 316 to select the

corresponding input channel

318, 318 a-n. Here, configuring the electrical multiplexing device 316 to select the corresponding input channel 318 causes the electrical multiplexing device 316 to transmit the corresponding electrical signal 310 to the electrical-to-optical converter 340, the electrical-to-optical converter 340 configured to convert the corresponding electrical signal 310 back to the corresponding optical signal 104. In some implementations, the electrical-to-optical converter 340 includes a burst-mode laser transmitter, which may include a Distributed Bragg Reflector (DBR) laser. Thus, the electrical-to-optical converter 340 may include bi-directional optical sub-assemblies (BOSAs) or transmitter optical sub-assemblies (TOSAs). The electrical-to-optical converter 340 may include an XGS-PON BOSA optically coupled to the corresponding OLT port 124. The electrical-to-optical converter 340 may also be in communication with an optical transmitter 322 that is optically coupled to a corresponding set of trunk optical fibers 110 via laser optics 304 in order to transmit the downstream optical signal 104 from the OLT port 124 to the PON 10. As described in more detail below with reference to fig. 5A and 5B, an active optical signal splitter 500 may be used to transmit the downstream optical signals 104 from the OLT ports 124 to the corresponding set of trunk fibers 110. In the example shown, active optical signal splitter 500 includes electrical-to-optical converter 340 and optical transmitter 322. As shown in fig. 5B, active optical signal splitter 500 can include a passive optical signal splitter 332 in place of optical transmitter 322 that receives the amplified optical signal 104 from fiber amplifier 300 optically coupled to OLT port 124. Other signal splitters 500 may also be used. In some examples, the corresponding trunk fibers 110, 110a aggregate optical coupling to respective burst-mode (BM) transmitters of ONUs 140 located at premises 152 of users 150.

In some embodiments, the O/E/O converter 300 includes controller circuitry 314 (e.g., controller electronics). The controller circuit 314 may be implemented in a Programmable Logic Device (PLD), such as a complex PLD (cpld) or a Field Programmable Gate Array (FPGA). The controller circuit 314 may be implemented in other forms, such as discrete logic devices. In the illustrated example, the optical signal receiver 305 (e.g., via the corresponding burst-mode limiting amplifier 312) may communicate a signal reception indication 324 to the controller circuit 314 when the corresponding optical signal 104 is received. For example, the burst-mode limiting amplifier 312 may communicate a signal reception indication 324 to the controller circuit 314 within 25 nanoseconds of the corresponding optical signal receiver 305 receiving the corresponding optical signal 104. In some examples, optical signal receiver 305 receives respective optical signals 104 in response to corresponding Burst Mode (BM) transmissions from respective ONUs 140. In some embodiments, the burst mode limiting amplifier 312 communicates the signal reception indication 324 to the controller circuit 314 only during burst mode transmissions. The burst-mode limiting amplifier 312 may stop transmitting the signal reception indication 324 to the controller circuit 314 within 100 nanoseconds of the end of the burst-mode transmission, i.e., when the O/E/O converter 300 stops receiving the respective burst-mode optical signal 104, 104a1-aN from the respective ONU 140. The signal reception indication 324 may cause the controller circuit to communicate a reset signal 326 to the transimpedance amplifier 308. The controller circuit 314 may adjust or manipulate the signal reception indication 324 to meet the requirements of the reset signal 326 for the transimpedance amplifier 308. In some embodiments, the controller circuit 314 transmits a reset signal 326 that is narrower than the signal reception indication 324 in order to complete the reset of the transimpedance amplifier 308 more quickly. In an example, the transimpedance amplifier 308 is reset within approximately 100 nanoseconds after receiving the respective optical signal 104. The controller circuit 314 may also widen the signal reception indication 324 to meet the requirements of the reset signal 326 on the transimpedance amplifier 308. As described in more detail below with reference to fig. 4A, the controller circuit 314 may include a signal conditioning circuit 400a for converting the signal reception indication 324 to a reset signal 326.

In some embodiments, the O/E/O converter 300 configures the electrical multiplexing device 316 based on the signal reception indication 324. In the illustrated example, the optical signal receiver 305 (e.g., via a corresponding burst-mode limiting amplifier 312) communicates a signal reception indication 324 to the controller circuit 314 upon receiving the respective optical signal 104. Based on the signal reception indication 324, the controller circuit 314 may transmit a channel selection indication 328 to the electrical multiplexing device 316 that identifies the corresponding input channel 318 of the electrical multiplexing device 316. The controller circuit 314 may adjust or manipulate the signal reception indication 324 to meet the needs of the electrical multiplexing device 316. In an example, the electrical multiplexing device 316 includes an ON semiconductor NB7VQ572M high performance differential 4:1 multiplexer. In some examples, each of the signal reception indications 324 received at the controller circuit 314 from each corresponding optical signal receiver 305 is logically combined by the controller circuit 314 to produce a channel selection indication 328. The controller circuit 314 may include a channel selection circuit 400B (fig. 4B, 4C) configured to logically combine the signal reception indications 324 to generate a channel selection indication 328. The controller circuit 314 may perform additional housekeeping functions 324 based on the signal reception indication, such as resetting or calibrating components at the appropriate time to maintain low noise and high signal fidelity.

In an example, within 100-. The electrical-to-optical converters 340 may be configured to convert the corresponding electrical signals 310 back to the respective optical signals 104. The electrical-to-optical converters 340 may transmit the respective optical signals 104 to the corresponding OLT ports 124. In some examples, the

optical signal

104, 104a includes a preamble pattern at the beginning of a burst mode transmission. The preamble pattern may be 700-800 nanoseconds long. In a further example, the

OLT ports

124, 124a receive the respective

optical signals

104, 104a at least 500 nanoseconds before the end of the transmission of the preamble pattern from the

ONUs

140, 140 a-n. In other words, the O/E/O converter 300 transmits the respective

optical signal

104, 104a to the

OLT port

124, 124a without losing information. In some examples, the operation of the O/E/O converter 300 is compatible with and suitable for use with commercially available OLTs 120.

Referring to fig. 3B, aN example O/E/O converter 300 is optically coupled to a corresponding set of trunk optical fibers 110 to receive respective burst mode optical signals 104, 104a1-aN from ONUs 140, 140a-n located at

premises

152, 152a-n of

subscribers

150, 150a-n via PON 10. In some examples, each trunk optical fiber 110 is associated with a respective optical signal receiver 305, 305 a-n. In these examples, each optical signal receiver 305 may include a

respective APD

302, 302a-n, a respective TIA308, 308a-n in communication with the APD 302, and a respective Limiting Amplifier (LA)312, 312a-n in communication with the TIA 308. Each LA 312 is configured to transmit a corresponding electrical signal 310 to a

corresponding input channel

318, 318a-n of an electrical multiplexing device 316. In the example shown, each LA 312 is configured to communicate a signal reception indication 324 to controller circuitry 314. Based on the signal reception indication 324, the controller circuit 314 may transmit a channel selection indication 328 to the electrical multiplexing device 316 that identifies the corresponding input channel 318 of the electrical multiplexing device 316. In an example, channel selection indication 328 identifies input channel 318 corresponding to LA 312, which communicates signal reception indication 324 to controller circuitry 314. Channel selection indication 328 may identify channel 318 corresponding to the highest priority LA 312 that communicated signal reception indication 324 to controller circuit 314. Other channel selection indications 328 based on the signal reception indication 324 are also possible. The controller circuit 314 may also communicate a reset signal 326 to the TIA 308.

In some examples, communicating the channel selection indication 328 to the electrical multiplexing device 316 causes the electrical multiplexing device 316 to transmit the corresponding electrical signal 310 to the electrical-to-optical converter 340. The electrical-to-optical converter 340 may include a burst-mode (BM) laser driver 344 capable of modulating a signal of a laser transmitter 346. In some examples, an Optical Subassembly (OSA) such as a transmitter OSA (tosa) or a bidirectional OSA (bosa) includes a laser transmitter 346. In an example, the electro-optic transducer 340 includes a 1270 nanometer TOSA 346. Other wavelength laser emitters 346 may also be used. Laser transmitter 346 may be an Externally Modulated Laser (EML) or a Directly Modulated Laser (DML). The laser transmitter 346 may be optically coupled to the

OLT ports

124, 124a to transmit the respective

optical signals

104, 104a to the OLT 120. In some examples, burst mode laser transmitter 346 includes a Distributed Feedback (DFB) laser. Other laser emitters 346 may also be used.

The O/E/O converter 300 may be installed at the CO 200 (FIGS. 1A-1C). In some examples, the components of O/E/O converter 300 are mounted on a Printed Circuit Board (PCB) and contained within a rack-mountable housing mounted at CO 200 or other convenient location. In some examples, the O/E/O converter 300 is installed at or near the RN 170 or the

premises

152, 152a-n of the

users

150, 150 a-n. Remote installation of the O/E/O converter 300 may extend the range of the OLT port 124. In some examples, O/E/O converter 300 is optically coupled to more than one OLT port 124 to provide redundancy for increased PON reliability. Redundant OLT ports 124 may be located at more than one CO 200 to avoid common mode faults, such as loss of power to OLT 120. The O/E/O converter 300 may be remotely configurable. In some examples, the O/E/O converter 300 includes data processing hardware 350 (e.g., processor(s) and/or controller (s)) and memory hardware 352 in communication with the data processing hardware 350 and storing instructions that, when executed by the data processing hardware 350, cause the data processing hardware 350 to execute a software application 352. The data processing hardware 350 may receive messages 354 transmitted over a communication 356 network. Message 354 may instruct data processing hardware 350 to reconfigure O/E/O converter 300. The data processing hardware 350 may selectively enable, disable, or otherwise configure or re-provide the single trunk optical fiber 110 or change the communication wavelength 104 of the optical signal. In the example, data processing hardware 350 responds to message 354, message 354 including a Simple Network Management Protocol (SNMP) command 354 transmitted from CO 200 via communication channel 356. In the event of a failure of one OLT port 124, the data processing hardware 350 may configure the O/E/O converter 300 to switch to operating the OLT port 124. In an example, the operational OLT port 124 is associated with a CO 200 that is different from the failed OLT port 124. In some examples, the data processing hardware 350 selectively enables/disables signals to/from the controller electronics 314.

Referring to fig. 4A, an example signal conditioning circuit 400a of the controller circuit 314 of fig. 3A and 3B is depicted. In the illustrated example, the signal conditioning circuit 400a includes a pulse generator configured to generate a reset signal 326 based on the signal reception indication 324 and to communicate the reset signal 326 to the TIA 308. Here, the circuit 400a includes at least one signal inverter, a parallel arrangement of a resistor R and a capacitor C, and an exclusive OR logic gate. In some examples, the controller circuit 314 transmits a reset signal 326 that is narrower than the signal reception indication 324 in order to more quickly complete the reset of the TIA 308. The width of the reset signal 326 may be based on the charging time of the capacitor C. The charging time may be based on the resistance of the resistor R and the capacitance of the capacitor C. In an example, the values of R and C produce a reset signal 326 that is 10 nanoseconds wide. Other signal conditioning circuits 314 may also be used, including signal inverters, delay circuits, and pulse stretchers.

Referring to fig. 4B, an example priority encoder circuit 400B of the controller circuit 314 of fig. 3A and 3B is depicted. In the illustrated example, the inputs to priority encoder circuit 400b are depicted as I (0) -I (3). Here, each input corresponds to a signal reception indication 324 from limiting amplifier 312. Each signal reception indication 324 corresponds to a respective MUX input channel. The outputs from priority encoder circuit 400b are depicted as O (0) and O (1). In the illustrated example, the channel selection circuit 400b includes a priority encoder circuit configured to generate the channel selection indication 318 based on the signal reception indication 324 for configuring the electrical multiplexing device 316 to select the corresponding input channel 318. For example, the priority encoder circuit 400b may adjust or manipulate the signal reception indication 324 to meet the needs of configuring the electrical multiplexing device 316. In an example, using AND gates, OR gates, AND NOT gates, the priority encoder circuit logically combines the four signal reception indications 324 to produce a two-bit channel selection indication 328 AND a validity signal V. The example circuit assigns the highest priority to the input channel 318 corresponding to input I (3) and the lowest priority to the input channel 318 corresponding to input I (0). The two-bit channel selection indication 328 encodes the number (0-3) of the highest priority input channel 318 associated with the signal reception indication 324. In an example, when the input channel 318 corresponding to I (3) is associated with the signal reception indication 324, the channel selection indication 328 encodes the decimal value three (binary 11). Table 1 below shows the relationship between input and output. The symbol X is used to represent an input having a state that is insignificant to the output.

TABLE 1

In some examples, only one ONU140, 140a-n transmits a burst-mode optical signal 104 at a time. In this case, priority encoder circuit 400b receives only one signal reception indication 324 at a time. The priority encoder circuit 400b may encode the number of the corresponding input channel 318 of the electrical multiplexing device 316 associated with the signal reception indication 324. The validity signal V indicates when the signal reception indication 324 is received by the priority encoder circuit 400 b. In some examples, the priority encoder circuit 400b communicates the validity signal V to the electrical multiplexing device 316 to signal the electrical multiplexing device 316 to select the corresponding input channel 318 encoded by the priority encoder circuit 400 b. The controller circuit 314 may include additional logic or other circuitry. In an example, the controller circuit 314 includes additional logic configurable to selectively enable or disable inputs to the priority encoder circuit 400b of the controller circuit 314. The controller circuit 314 may also widen, narrow, or invert the input signal. Fig. 4C depicts another priority encoder circuit 400C, 314, including additional AND gates configured to selectively enable the signal reception indication 324. Here, the ENABLE signal, depicted as ENABLE1-ENABLE4, may selectively mask or disable the corresponding signal reception indication 324 such that the corresponding signal reception indication 324 has no effect on the priority encoder circuit 400 b. In some examples, signal reception indication 324 is disabled unless a corresponding enable signal is asserted. The selectively enabled channel may be used to support the redundant OLT ports 124 for increased reliability.

Referring to fig. 5A, active optical signal splitters 500, 500a are depicted. Here, the active optical signal splitter 500a converts the downstream optical signals 104 from the

OLT ports

124, 124a into corresponding electrical signals 310, copies the corresponding electrical signals 310, and restores each copied corresponding electrical signal to a copy of the optical signal 104. The active optical splitter 500a of fig. 5A may be referred to as an optical/electrical/optical (O/E/O) splitter. In the illustrated example, the

OLT ports

124, 124a are optically coupled to the optical transmitters 322, 322_1-NA connected optical transceiver 340. The optical transceiver 340 may be a laser transceiver of an Optical Subassembly (OSA), such as a receiver OSA (rosa) or a bidirectional OSA (bosa). The optical transmitter 322 may be optically coupled to a corresponding set of trunk optical fibers 110, 110a to transmit the downstream optical signals 104, 104a1-aN from the

OLT ports

124, 124 a. In some examples, the optical transceiver 340 receives the downstream

optical signals

104, 104a to be transmitted in a Continuous Mode (CM) from the

OLT ports

124, 124a, converts the

optical signals

104, 104a into corresponding electrical signals 310, and transmits a copy/duplication of the corresponding electrical signals 310 to each

optical transmitter

322, 322_1-N. Each optical transmitter 322 is configured to convert the corresponding electrical signal 310 back into an

optical signal

104, 104a and transmit the optical signal 104 to the corresponding ONU140 via the corresponding trunk optical fiber 110. In an example, the light emitter 322 includes 1577 nanometer TOSA. Other wavelengths of light emitters 322 may also be used. The optical transmitter 322 may include an Externally Modulated Laser (EML) or a directly modulated transmitter (DML). In an example, the optical transmitter 322 includes an AST-EML-1577-10G-L600-V1 Distributed Feedback (DFB) laser diode with an integrated electro-absorption modulator (EAM) that provides a single longitudinal mode at 1577 nm.

In some examples, the active optical signal splitter 500a extends the range of the corresponding OLT port 124 by increasing or restoring the optical signal strength transmitted from the OLT port 124 to a remote location. In some examples, each light emitter 322, 322₁-322_NSubstantially equal to the optical power output of the

OLT ports

124, 124 a. Thus, each optical transmitter 322 may be via a corresponding trunk optical fiber 110FT_a1-FT_aNTo transmit a corresponding optical signal 104, 104a1-nN that is a substantial copy/duplication of the original

optical signal

104, 104a output from the

OLT port

124, 124a at substantially the same optical power level. In other words, unlike a passive optical splitter, the power of the

optical signals

104, 104a emitted by the

OLT ports

124, 124a is not being transmitted by the respective trunk fibers FT_a1-FT_aNEach optical signal 104 that is distributed is divided, split, or shared between them.

Referring to fig. 5B, another active optical signal splitter 500, 500B is depicted. In contrast to the O/E/O approach implemented by the active optical signal splitter 500a of fig. 5A, the active optical signal splitter 500b uses active optical components to split the downstream optical signal 104 from the

OLT ports

124, 124a, rather than converting the optical signal 104 into a corresponding electrical signal 310. In the illustrated example, active optical signal splitter 500b includes a passive optical splitter 332 and an optical amplifier 330 in place of optical transceiver 340. Optical amplifier 330 may include a power or active optical amplifier. Here, the optical amplifier 330 receives the optical signal 104 from the OLT port 124 and outputs the amplified optical signal 104_A. Optical amplifier 330 may comprise an Erbium Doped Fiber Amplifier (EDFA). For example, optical amplifier 330 may include an L-band EDFA. However, other wavelengths of optical amplifier 330 may be used. In the illustrated example, the

OLT ports

124, 124a are optically coupled to an optical amplifier 330. For optical amplifier 330Pump, boost the power of, or otherwise amplify the intensity of the optical signal 104 emitted from the

OLT port

124, 124a to produce the amplified optical signal 104_A. Amplified optical signal 104A is launched into a passive optical splitter 332 optically coupled to optical amplifier 330. In the example, passive optical splitter 332 is a 1:4 splitter. In other words, the optical splitter 332 splits the amplified optical signal 104_ASplit into four split optical signals 104_S. In some examples, each optical signal 104 split by passive optical splitter 332_SIncluding one quarter of the power of amplified optical signal 104 received by passive optical splitter 332. In some configurations, the optical amplifier 330 is configured to amplify the optical signal 104 output from the OLT port 124 by an amplitude proportional to the splitting ratio of the splitter 332. For example, when splitter 332 comprises a 1:4 splitter, optical amplifier 330 may increase the power level of optical signal 104 output from OLT port 124 by an amplitude of four (4). Other splitter configurations may also be used. In other examples, the optical signals 104 are optically split by a splitter 332 before being pumped by the respective fiber amplifiers 330. For example, 1:4 passive optical splitter 332 can be directly optically coupled to OLT port 124a to receive downstream optical signal 104a and split it into four split optical signals 104_SWhereby a respective fiber amplifier 330 amplifies each respective split optical signal 104 output from splitter 332_S. Here, each respective fiber amplifier 330 may split each respective branched optical signal 104_SAmplifies an amplitude proportional to a splitting ratio of the splitter 332. Other configurations of active and passive optical elements may also be used.

In some examples, splitter 332 (or corresponding amplifier 330 when splitter 332 is located upstream of amplification) splits

optical signals

104, 104_STo a corresponding Variable Optical Amplifier (VOA) 334. Each corresponding VOA 334 may be controlled at each respective trunk fiber FT_a1-FT_aNThe power level of the upper emitted optical signal 104. In an example, the VOA 334 enables or disables the trunk fiber FT at each respective trunk fiber FT_a1-FT_aNUp-emitted optical signal 104. 104a 1-aN. Any of the active optical signal splitters depicted in fig. 5A and 5B may be used in conjunction with the O/E/O converter 300. In other words, both the optical design and the O/E/O design are compatible with the O/E/O converter 300. Other configurations of the active optical signal splitter are possible.

Fig. 6 provides an example arrangement of operations of a method 600 for combining optical signals from trunk fibers into an optical signal. At operation 602, the method 600 includes receiving a respective optical signal 104 at a respective optical signal receiver 305 optically coupled to a respective trunk optical fiber 110. At operation 604, the method 600 includes determining, by the corresponding optical signal receiver 305, when each respective optical signal 104 is received. At operation 606, the method 600 includes converting, by the corresponding optical signal receiver 305, the corresponding optical signal into a corresponding electrical signal 310. At operation 608, the method 600 includes transmitting, by the corresponding optical signal receiver 305, the corresponding electrical signal 310 to the corresponding input channel 318 of the electrical multiplexing device 316. At operation 610, the method 600 includes configuring the electrical multiplexing device 316 to select a corresponding input channel 318. At operation 612, the method 600 includes causing the electrical multiplexing device 316 to transmit the corresponding electrical signals 310 to the electrical-to-optical converter 340, the electrical-to-optical converter 340 configured to convert the corresponding electrical signals 310 back to the respective optical signals 104.

A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

Claims

1. A method (600) comprising:

receiving respective optical signals (104) at respective optical signal receivers (305) optically coupled to respective trunk fibers (110);

determining, by the corresponding optical signal receiver (305), when each respective optical signal (104) is received; and

for each corresponding optical signal receiver (305), when the respective optical signal (104) is received:

converting, by the corresponding optical signal receiver (305), the respective optical signal (104) into a corresponding electrical signal (310);

transmitting, by the corresponding optical signal receiver (305), the corresponding electrical signal (310) to a corresponding input channel (318) of an electrical multiplexing device (316); and

configuring the electrical multiplexing device (316) to select the corresponding input channel (318), causing the electrical multiplexing device (316) to transmit the corresponding electrical signal (310) to an electrical-to-optical converter (340), the electrical-to-optical converter (340) configured to convert the corresponding electrical signal (310) back to the respective optical signal (104).

2. The method (600) of claim 1, wherein each corresponding optical signal receiver (305) comprises:

a photodiode (302) optically coupled to a corresponding trunk fiber (110), the photodiode (302) converting the respective optical signal (104) into a respective current signal (306);

a transimpedance amplifier (308) in communication with the photodiode (302), the transimpedance amplifier (308) converting the respective current signal (306) into the corresponding electrical signal (310); and

a burst mode limiting amplifier (312) in communication with the transimpedance amplifier (308), the burst mode limiting amplifier (312) indicating when the respective optical signal (104) is received.

3. The method (600) of claim 2, wherein in response to determining when the respective optical signal (104) is received, the burst mode limiting amplifier (312) transmits a reset signal (326) to a signal conditioning circuit (400a) causing the signal conditioning circuit (400a) to reset the transimpedance amplifier (308).

4. The method (600) of claim 3, wherein communicating the reset signal (326) to the signal conditioning circuit (400a) comprises communicating the reset signal (326) to a Complex Programmable Logic Device (CPLD) or a Field Programmable Gate Array (FPGA).

5. The method (600) of claim 2, wherein the photodiode (302) comprises an avalanche photodiode or a PIN diode.

6. The method (600) of any of the preceding claims, wherein configuring the electrical multiplexing device (316) to select the corresponding input channel (318) comprises communicating, by the corresponding optical signal receiver (305), a signal detection indication to a channel selection circuit (400b), causing the channel selection circuit (400b) to communicate a channel selection indication (328) to the electrical multiplexing device (316), the channel selection indication (328) identifying the corresponding input channel (318) of the electrical multiplexing device (316).

7. The method (600) of any of the preceding claims, wherein the electrical-to-optical converter (340) comprises a burst-mode laser emitter.

8. The method (600) of claim 7, wherein the burst mode laser transmitter comprises a distributed bragg reflector, DBR, laser.

9. The method (600) of any of the preceding claims, further comprising transmitting, by the electrical-to-optical converter (340), the respective optical signal (104) to a port (124) of an optical line termination, OLT, (120).

10. The method (600) of any of the preceding claims, wherein the corresponding trunk optical fiber (110) is optically coupled to a respective burst-mode laser transmitter (346) of a respective optical network unit, ONU (140).

11. An optoelectronic light converter comprising:

an electrical multiplexing device (316) comprising one or more input channels (318); and

an optical signal receiver (305) optically coupled to a corresponding trunk fiber, each optical signal receiver (305) configured to:

receiving respective optical signals (104) from the corresponding trunk optical fibers;

determining when the respective optical signal (104) is received; and

when the respective optical signal (104) is received:

converting the respective optical signals (104) into corresponding electrical signals (310);

transmitting the corresponding electrical signal (310) to a corresponding input channel (318) of an electrical multiplexing device (316); and

12. The optical-to-electrical optical converter of claim 11, wherein each corresponding optical signal receiver (305) comprises:

a photodiode (302) optically coupled to a corresponding trunk fiber, the photodiode (302) converting the respective optical signal (104) to a respective current signal (306);

13. The opto-electrical-to-optical converter of claim 12, wherein in response to determining when the respective optical signal (104) is received, the burst-mode limiting amplifier (312) transmits a reset signal (326) to a signal conditioning circuit (400a) causing the signal conditioning circuit (400a) to reset the transimpedance amplifier (308).

14. The optoelectronic to optical converter as recited in claim 13, wherein the signal conditioning circuit (400a) comprises a Complex Programmable Logic Device (CPLD) or a Field Programmable Gate Array (FPGA).

15. The optoelectronic to optical converter as recited in claim 12, wherein the photodiode (302) comprises an avalanche photodiode or a PIN diode.

16. The optical-to-electrical optical converter of any one of claims 11-15, wherein configuring the electrical multiplexing device (316) to select the corresponding input channel (318) includes, by the corresponding optical signal receiver (305), communicating a signal detection indication to a channel selection circuit (400b), causing the channel selection circuit (400b) to communicate a channel selection indication (328) to the electrical multiplexing device (316), the channel selection indication (328) identifying the corresponding input channel (318) of the electrical multiplexing device (316).

17. The opto-electrical-optical converter according to any of claims 11-16, wherein the electro-optical converter (340) comprises a burst mode laser emitter.

18. The optoelectronic optical to electrical converter of claim 17, wherein the burst-mode laser transmitter comprises a distributed bragg reflector DBR laser.

19. The optical-to-electrical optical converter according to any of claims 11-18, further comprising a port (124) for transmitting the respective optical signal (104) by the electrical-to-optical converter (340) to an optical line termination, OLT, (120).

20. The opto-electrical optical converter according to any of claims 11-19, wherein the corresponding trunk optical fiber (110) is optically coupled to a respective burst-mode laser transmitter (346) of a respective optical network unit, ONU (140).